1. Field of the Invention
The present invention relates to a novel substituted carboxanilide derivative and a plant disease control agent comprising the same as an active ingredient.
2. Description of the Related Art
The plant disease control agent which has been developed in recent years and has a selective activity differs from conventionally used, nonselective, plant disease control agent and can exhibit steady effect at a low dosage. However, the plant disease control agent has a problem caused by the development of a resistant fungus leading to a reduction in efficacy.
For example, a benzimidazole-based fungicide has a wide fungicidal spectrum and exhibits excellent effect also on gray mold. However, such fungicide experienced in the 1970's a drastic reduction in efficacy due to appearance of a resistant fungus. A dicarboximide-based fungicide received attention as a replacement for the benzimidazole-based fungicide. Nevertheless, a resistant fungus also appeared in the 1980's against the dicarboximide-based fungicide. Consequently, the counter-measure for controlling the resistant fungus of gray mold has become a serious problem in the world.
On the other hand, an azole-based fungicide has a wide fungicidal spectrum and is an excellent fungicide which exhibits efficacy at a hitherto unexpectedly low dosage particularly for powdery mildew and rust of various crops and scab of apple and pear. However, a resistant fungus against this pesticide has recently appeared and also led to a problem of sharp reduction in the pesticide efficacy. The application number of the fungicide also tends to be limited.
Thus, appearance of the fungicide resistant fungus has become an inevitable problem for the selective plant disease control agent, and accordingly development of a new fungicide is now an urgent subject.
Further, a plant is generally infected by various species of diseases. Representative diseases to be controlled include, for example, blast, sheath blight and other rice diseases, gray mold, powdery mildew and other diseases of cucumber and strawberry; and so as to fruit trees, black spot, scab, rust, powdery mildew and other diseases of pear; and alternaria leaf spot, scab, Podosphaera leucotricha and other apple diseases. Even though the generation of these diseases overlaps seasonally, it is generally difficult to control these diseases by single formulation of the fungicide. Accordingly, in recent years, compounds having fungicidal activity are frequently used as a mixture for practical application. As the result, even though the amount of each fungicidally active ingredient in the mixture is small, the total amount of the active compounds to be used generally becomes considerably large. It is assumed in such a case that, when a fungicide which is capable of controlling various species of diseases by single use and is effective even at a low dosage is developed, the field of application will be broad due to excellent efficacy and reduction of adverse effect on the environment.
Several aromatic carboxanilide derivatives have been conventionally known to exhibit fungicidal activity. For example, European Patent A-545099 has recently disclosed that a carboxanilide derivative represented by the formula below has efficacy for Botrytis cinerea; ##STR2## wherein R is an alkyl which has 2-12 carbon atoms and can be halogenated, an alkenyl which has 3-12 carbon atoms and can be halogenated, an alkynyl having 3-6 carbon atoms and can be halogenated, an alkoxy which has 2-12 carbon atoms and can be halogenated, an alkenyloxy which has 3-12 carbon atoms and can be halogenated, an alkynyloxy which has 3-12 carbon atoms, a cycloalkyl which has 3-6 carbon atoms and can be substituted by an alkyl having 1-4 carbon atoms, a cycloalkenyl which has 4-6 carbon atoms and can be substituted by an alkyl having 1-4 carbon atoms, a cycloalkyloxy which has 5-6 carbon atoms and can be substituted by an alkyl having 1-4 carbon atoms, a cycloalkenyloxy which has 5-6 carbon atoms and can be substituted by an alkyl having 1-4 carbon atoms, a phenyl which can be susbstituted by an alkyl having 1-4 carbon atoms, an alkoxy having 1-4 carbon atoms, an alkylthio having 1-4 carbon atoms or halogen, Y is pyridin-3-yl substituted in the 2-position by a halogen, methyl, trifluoromethyl, methoxy, methylthio, methylsulfinyl or methylsulfonyl; phenyl substituted in the 2-position by a methyl, trifluoromethyl, chlorine, bromine or iodine; 2-methyl-5,6-dihydropyran-3-yl, 2-methyl-5,6-dihydro-1,4-oxathiin-3-yl, 2-methyl-5,6-dihydro-1,4-oxathiin-3-yl-4-oxide, 2-methyl-5,6-dihydro-1,4-oxathiin-3-yl-4,4-dioxide; 2-methylfuran-3-yl substituted in the 4- and 5-positions by a hydrogen or methyl; thiazol-5-yl substituted in the 2- and 4-positions by hydrogen, methyl, chlorine or trifluoromethyl; thiazol-4-yl substituted in the 2- and 5-positions by hydrogen, methyl, chlorine or trifluoromethyl; 1-methylpyrazol-4-yl substituted in the 3- and 5-positions by methyl, chlorine or trifluoromethyl; oxazol-5-yl substituted in the 2- and 4-positions by hydrogen, methyl or chlorine.
Further, European Patent A-589301 has disclosed that a carboxanilide derivative represented by the formula below has efficacy for Botrytis cinerea; ##STR3## wherein R is an alkyl which has 3-12 carbon atoms and can be partly or completely halogenated, alkoxy having 2-12 carbon atoms, alkenyl having 3-12 carbon atoms, alkenyloxy having 3-12 carbon atoms, alkynyl having 3-6 carbon atoms, alkynyloxy having 3-6 carbon atoms, cycloakyl which has 3-7 carbon atoms and can have one to three alkyls having 1-4 carbon atoms, cycloalkenyl having 4-7 carbon atoms, cycloalkyloxy having 3-7 carbon atoms, cycloalkenyloxy having 4-7 carbon atoms, and phenyl group which can carry one to five halogens and/or one to three of the following radicals; alkyl having 1-4 carbon atoms, haloalkyl having 1-4 carbon atoms, alkoxy having 1-4 carbon atoms, haloalkoxy having 1-4 carbon atoms, alkylthio having 1-4 carbon atoms and haloalkylthio group having 1-4 carbon atoms; and Y is a cyclic group represented by either one of the formulas Y.sub.1 to Y.sub.5 below: ##STR4## wherein D is a hydrogen atom or alkyl having 1-4 carbon atoms, E is a halogen atom or alkyl having 1-4 carbon atoms, G is an alkyl having 1-4 carbon atoms or haloalkyl having 1-4 carbon atoms, and n is an integer of 1 or 2.
European Patent A-545099 and A-589301 include very broad range of compounds as the highest concept. However, the compounds described in the examples are limited. For example, in the carboxanilide compounds described in these gazettes, the alkyl group which has been specifically described on the examples and tables as a substituent on the 2-position of the aniline ring is restricted to a straight alkyl having 3-7 carbon atoms; isopropyl, sec-butyl, tert-butyl, 1-methylbutyl, 1-methylhexyl and other alkyl groups which are branched at the .alpha.-position; and isobutyl, 2-ethylbutyl and other alkyl groups which are branched at the .beta.-position. No description is found at all on the alkyl group which is branched at the .gamma.-position.
The present inventors have tested control activity against various species of plant-pathogenic fungus concerning the specifically disclosed compounds in these gazettes. As a result, neither of the compounds tested had control effect against rice blast. Some compounds had quite no efficacy against Powdery mildew and gray mold. Even though in the case of compounds having efficacy, the effect was very weak.